1. Field of the Invention
The invention relates to mirrors for automotive vehicles. In one aspect, the invention provides an improved mass configuration to the mirror assembly which allows for lower moments of inertia in the direction of travel of the mirror. In another aspect, the invention relates to a motor assembly utilizing a single motor with selection of the axis of the mirror being adjusted based upon the rotational speed of the motor.
2. Description of the Related Art
Side view mirrors are standard equipment on automotive vehicles. Frequently, the side view mirrors include mirrors on both the driver's side and the passenger's side of the vehicle. The passenger's side mirror will be difficult for the driver to manually adjust. Furthermore, manual adjustment of either mirror will require the operator to lower the window, exposing the operator and the interior of the vehicle to inclement weather. These problems have been solved by mirrors which can be adjusted by the operator from inside the vehicle.
Remote mirror adjustment typically involves tilting the mirror about a vertical axis and a generally perpendicularly-oriented horizontal axis through a motorized assembly typically employing two electric motors to control movement of the mirror about the two axes. One motor is used to tilt the mirror along the vertical axis. The other motor used to tilt the mirror along the horizontal axis. The output from the motors drives jackscrews connected to the mirror which move linearly to tilt the mirror.
The use of two motors adds cost and weight to the mirror. The mirror housing must also accommodate the volume occupied by the motors, expanding the profile of the mirror. Additionally, the motors can fail, thereby requiring replacement. The use of two motors increases the probability of a motor failure as compared to a mirror having only one motor.
A single motor actuator solves some of the problems attending the use of a two motor actuator. However, a sophisticated clutch assembly must be used to selectively transfer motor output to one or both the jackscrews in order to obtain the desired tilting of the mirror. The clutch assembly is frequently fabricated of plastic components in an attempt to optimize the weight and cost of the mirror assembly. However, the performance of the plastic components can be affected by the ambient temperature, leading to undesirable performance of the mirror tilt function. Further, these devices often include solenoids to interconnect the motor with a particular jackscrew, adding weight and increasing the probability of a malfunction due to failure of the solenoids.
While a single motor can be used to control both the vertical and horizontal movement of a mirror element, the relative location of the horizontal and vertical tilt actuators, pivot points, and axes of rotation necessary to provide a desired level of adjustment results in an assembly having a relatively large size. This size is unacceptable for some mirrors, particularly those used with smaller vehicles, such as compact cars.
It is common to pivot or fold the external mirror against the vehicle body to prevent the jarring of the mirror when the vehicle is not operated. The mirror folding function can incorporate a power assist, such as that disclosed in U.S. Pat. No. 5,684,646. External mirrors are also extendable away from the vehicle, which is useful when towing a trailer. Mirrors incorporating both the powered fold and powered extension functionality are known and have used separate motors for both the folding and extension functions. Examples of such mirrors are disclosed in U.S. Pat. Nos. 6,276,808 and 6,213,609, assigned to the assignee of the current application, and are incorporated by reference.
The use of separate motors for dual function applications such as folding and extending the external mirror is not desirable because it increases costs and part count, which are undesirable characteristics in the automotive parts supply industry. The extra motor also increases the volume of the mirror housing, which is also typically undesirable since increased volume can lead to increased drag, which negatively impacts fuel mileage, and increased wind-induced noise.
There are various ways of selecting which actuator is to operate in order to tilt the reflective element along a selected axis. One way is to selectively operate one or both actuators using a clutch assembly which is engaged or disengaged based upon the angular velocity of the motor.
Difficulty arises in selecting and maintaining the proper motor speed for the actuator assembly to properly operate. Complicated electromechanical devices for controlling the motor speed add cost and weight to the mirror assembly, and increase the likelihood that the tilt mechanism will fail, thereby requiring costly replacement. Furthermore, such devices can wear over time, with a consequent drop-off in performance.
While the use of a single motor and speed-activated clutch provides a simple, durable tilt actuator, it may be necessary at times to replace the motor assembly/actuator. Conventional design of rearview mirrors incorporating such a system requires that the mirror be disassembled in order to remove and replace the actuator. This requires costly technician time, and removal of the vehicle from service during the repair. Additionally, reassembly of the mirror must be done accurately in order to ensure that the mirror operates properly after the repair has been completed. It is not always possible to reassemble the mirror without introducing performance deficiencies which can lead to additional repair activities.